Citrix XenServer 5.6: Virtual Machines In Motion

What percentage of servers shipped to market are now virtualized? Take a guess: Seventy percent? Eighty percent? Ninety?

Not even close, folks. According to a survey by research firm IDC earlier this year, fewer than one in five servers shipped to market in 2009 were virtualized -- although, IDC says, virtualization remains a priority for enterprises. That's particularly true in the x86 server environment, where advances by Intel and Advanced Micro Devices have made virtualization more cost-effective than ever.

There does remain, however, lots of good data about how the three big players in virtualization have been faring in the marketplace. While VMware has long been the top dog in this technology, Citrix with its XenServer platform and Microsoft with its Windows Server 2008 and Hyper-V have both provided very strong offerings.

With so few players in enterprise virtualization, and the total addressable market and opportunity mind-numbingly vast, VMware, Citrix and Microsoft will all do well as long as they continue to provide upgrades, channel engagement and attention to market needs. Different solutions will appeal to different solution providers and different enterprises.

For this month's issue, the CRN Test Center looked under the hood of Citrix's XenServer 5.6 and found that, at the very least, it's keeping up with its competitors. At most, the free, downloadable virtualization solution can offer a quick way to create a series of virtual machines based on several flavors of Linux or Windows, from Red Hat Linux to SuSE Enterprise Linux Server.

As with previous versions of XenServer, this version is quick to install and includes a number of different "templates" for Linux or Windows operating systems -- all designed to streamline the process of creating or cloning virtual machines. As with past versions of XenServer, we tested this version on a Hewlett-Packard ProLiant server running a single-core Xeon processor with 2 GB of RAM -- minimal, legacy hardware. This version of XenServer is optimized to work with Citrix's XenMotion software, which allows for hot migration of virtual machines from one host server to another without the need to power down a server. XenMotion is powerful, but it's not fully baked for all operating systems.

For example, there is a "known issue" in using XenMotion to migrate virtual machines running SLES 11 without having it fail in process, which is expected to smooth out on further kernel releases from Novell.

In the CRN Test Center Lab, we found XenCenter worked well. However, XenServer 5.6, despite advances and inclusion of several additional and up-to-date virtual machine templates (including, for example, SLES 11 and Windows 7), is not as streamlined as either of its main rivals -- VMware or Hyper-V. The need to install a separate Linux Pack, for example, before quickly creating a Linux virtual machine adds a few more steps that you don't need to take in either VMware or Hyper-V. There are also too many instances when line commands are required for functions that are automated or included in a GUI or wizard in VMware or Hyper-V.

So while XenServer 5.6 adds more powerful management capability with XenMotion integration, it does add complexity, which, as everyone knows, is a particular enemy of many small or midsize enterprises.

We like, and can recommend, XenCenter 5.6 as an incremental improvement over earlier versions, with the additional power of integration with XenMotion. Over time, we expect XenMotion to become a killer virtualization app -- if developers can simplify it and glitches (like with SLES 11) are smoothed over.

However, cost gains that are realized because XenServer is free could be lost in the additional complexity it provides if not managed correctly.

With fewer than one in five servers virtualized, there is a lot of headroom for growth. How quickly that number grows could depend on how Citrix addresses the complexity issues and other bumps in XenServer and XenMotion.